This terminological debate is influenced by Allied, but especially American, propaganda during the war and shortly after it, that sought to draw a (largely imaginary) distinction between "Germans" and "Nazis".

The chief impetus for this linguistic distinction, especially in the 1940s, was that a very large percentage of the population of the United States was of whole or partial German ancestry -- even today, close to 17% of the total population of the United States self-reports German ancestry. On the whole, the German-Americans were relatively well-assimilated into the "white" ethnic grouping of the time.

Thus, any propaganda animus against "Germans" was likely to run afoul of positive "Hey my Grandma was German" feelings among the white population of the United States. Therefore, it was politically convenient to draw a distinction in war-time discourse and propaganda between "Germans" and "Nazis". This over-emphasis on the distinction between "Nazis" and the rest of the German population is well-documented, and almost certainly contributed to the persistent myth of the "clear Wehrmacht".

The above is selectively summarized from "The Nazis and U.S. Foreign Policy Debates: History, Lessons, and Analogies" by M.H. Moore, published quite recently U.S. Foreign Policy and the Other (2014?)

I would personally frown upon the practice, and seeing its use in a work would likely raise questions in my mind. Looking at the project you cited, the creator uses that terminology heavily- there's a lot of 'fighting the Nazis', 'Nazi soldiers', etc., though I did hear at least one 'German army'. He even gets to the point of saying that "half a million Nazis would ultimately die in Stalingrad", which is just patently false, because of course they weren't all Nazis. The whole thing seems to be very heavily simplified, and I imagine it is aimed at an audience which has minimal familiarity with the events of the war. There are other things that jump out at me: one example, Yugoslavia's military deaths are listed as coming from "guerrilla fighting, civil conflict, and mass executions"- so ethnic nationalists or anti-communists fighting other forces within the nation are war-related? And 'mass executions' leads into gray territory, because even ignoring the question of when partisans are soldiers, you can't separate out partisan deaths from civilians in that context. From there, he goes on to count deaths in the gulag as Soviet civilian casualties! Should we also include the Bengal famine, then? The graphic shows a million+ Indian civilian casualties, but there's never a breakdown and there's no number shown, so it's impossible to know. Doesn't look like it gets anywhere near 3 million, but then where did all those deaths come from?

Moving on to the so-called "Long Peace", it's stated that there has been no post-WWII conflict in Europe other than the Soviet invasion of Hungary. Well, just for starters, there's the Prague Spring and subsequent invasion, and how did he miss all the wars in the Balkans? And the overall graph of post-war casualties misses by a huge margin- the Second Congo War alone probably has led to more deaths than that graph shows for the past 50 years. It's like this guy is including every single death he can for WWII and then ignoring all the subsequent ones in order to prove some point. Funny how that happens.

So, I've totally diverged from the topic at hand here. I guess what I want to say is, I see this usage as occurring in sort of 'history lite' contexts- TV, shoddy books, and Internet amateurs. I wouldn't call something like the cited website "semi-professional"- just because it has good design doesn't make it necessarily accurate or informative. Most books, even popular history, probably would use 'German' instead of 'Nazi'- I wouldn't even expect that from a Bill O'Reilly-caliber source, though I admit I have not yet read such classics as 'Killing Patton'. And of course, the caveat here is that this is just in my personal experience, and perhaps there are scholarly and well-researched works that would say 'Nazi soldiers', though I would tend to doubt it.

It depends on how you look at the question. Were all Wehrmacht soldiers by extension also Nazi soldiers because their leadership reported to the NSDAP or do we judge them based on whether or not that specific soldier was a member of the Nazi party? I think, based on the logical consequence of what we name members of other armed forces around that time, it wouldn't make much sense to indeed label all German soldiers as Nazi soldiers. Although it is not unconventional (nor particularly conventional) to refer to all Italians fighting in the war as Fascists, or all (non-communist/warlord-tied) Chinese as Kuomintang, calling all US or British men and women fighting in the war as 'Democrat' or 'Conservative' soldiers seems incredibly odd. Why then, by extension, should we label Wehrmacht soldiers Nazis if we apply a different distinction between political party and armed forces in other states?

I think labelling all Wehrmacht soldiers as Nazis also oversimplifies the conflict as something black and white, between good and evil. By collectively vilifying the Germany in WWII, you are also absolving it collectively of that role after the war ended, once the party was dissolved. I think this is wrong, as many individuals who did indeed commit war crimes lived on after the war and did not rescind their views, even though we could not longer call them 'Nazis' by the definition of merely serving the establishment.

Collectively labelling an entire group or nation also causes different complications. Are individuals who are conscripted against their will and fought for the Nazis, by extension also Nazis? Is a man who fought in the Wehrmacht solely to save his family from political repercussions a Nazi? How about teenagers indoctrinated in the Hitler Jugend, who often fought in the final months of the war? Wehrmacht officers like von Stauffenberg who actively tried to resist the leadership? Do all of these people stop being Nazis after the war is finished or does the label follow them to the grave?

Although I understand why some might refer to all German soldiers in the war as Nazis, it is an oversimplification that is not necessary and can only cause harm and confusion. I strongly believe that the only soldiers during WWII that we should refer to as Nazis are those with NSDAP membership.

Interesting question. I like it a great deal, but the perspective on the question will vary widely depending on the historian. And admittedly I'm not a German historian, I mostly focused on British Empire, but have read more than most of WW2 and am comfortable giving you a place to start.

For starters, it depends on the division. The German armed forces, although all ultimately reporting to the Nazi party and the Fuhrer, were Nazi-fied psychologically to varying degrees.

You need to understand the strict military culture of the German armed forces. It's really unlike anything you'd see in modern culture, pure German Warriors. I'd start with something like Field Marshall Erich von Manstein's "Lost Victories: The War Memoirs of Hitler's Most Brilliant General". Manstein viewed the entire conflict as an entirely operational matter. Completely avoided the topics of genocide, politics, and everything we'd associate with Nazis. He was a soldier serving the legitimate government. End of argument. I wouldn't consider von Manstein a Nazi. He was soldier. Much has been written about the "clean war" fought by the German Army. Wolfram Wette in "The Wehrmacht: History, Myth, Reality, argues against the clean war theorem and disregards it as propaganda created by officers trying to save face after the war. Finding anti-semites in 1930s/40s wasn't exactly difficult, so either way it's certainly an interesting question if the army was a Nazi force or not.

On the other end of the spectrum, you have the SS, specifically the Einsatzgruppen. These were Nazi loyal foot soldiers. There is no clean SS theorem because these soldiers were dirty and proud of it. I remember reading Richard Rhodes, "Masters of Death: The SS-Einsatzgruppen and the Invention of the Holocaust" when it first came out. Details are getting vague (I'm possibly conflating), but IIRC he stayed away from the post-1943 final solution and focused on the hands on aspect of the mass executions. Few books will give you a view into of the violence, in some ways even worse than the Holocaust itself, not in scope but in the shear brutality of hands on killing and body disposal. These are your unquestionably Nazi foot soldiers.

TL;DR: A possible argument could be made for the main army as "German Soldiers" and not "Nazi soldiers," but much of the special forces were selected by Nazis as true believers.

It's an interesting concept. And I won't be able to touch the depth here, but those books will give you a start.

What is the stance of (English-speaking) historians on that?

No historian of the Third Reich (/related topic) refers to German soldiers as "Nazi soldiers". It's that simple - to do otherwise is to be guilty of a misleadingly inaccurate generalization.

Is the former KPD activist drafted into the Wehrmacht, only to desert to the Red Army, a 'Nazi soldier'? Prior to the Nazi capture of power, a full third of the German voting population was solidly aligned with the socialist left - despite (and because of) persecution and suppression the vast majority of these people went on to fill one role or another in NS Germany (including the military), were they then Nazis? Can one espouse Marxist ideals and still be a Nazi?

Then there were those often energetic servants/accomplices of the NS regime who were quite plainly contemptuous of the real Nazis - Gestapo chief Heinrich Müller, head of OKH Franz Halder (and really, the vast majority of Wehrmacht generals - but this does not imply 'clean hands'), but who nevertheless held views which were at least partly consistent with Nazi ideology, such as violent anti-communism, and bottomless contempt for democracy and liberalism. Can one despise and ridicule Hitler and still be a 'Nazi'?

And if these people are undoubtedly still Nazis, what then do we call those people who were fanatical adherents to NS ideology and Hitler himself? 'Super-Nazis'?

Very surprising there is any debate on this at all here - I can't think of a single academic historian ever having transgressed thus, and that's pretty much the end of the story.

To add to this question, wouldn't referring to the common German soldiers as "Nazis" be like referring to Americans soldiers under the Obama administration as "Democrats"?

edit: Downvotes? Really? Was my question too obvious?